[IDEA] Add meaningful error messages when user tries to import an invalid assembly function

[macabeus]

Is your feature request related to a problem? Please describe.

If the user tries to import an invalid assembly function, it receives a hieroglyphic error message.

Describe the solution you'd like

Instead, we should provide an error message that describes the issue in few words and how to fix it.
For example:

1. Warn that it's from a tool like Ghidra, Binary Ninja or IDA, which may have changed the assembly function and aren't a good source, and suggest a better way to get the code
2. Ask to remove the line numbers
3. Detect that it's missing the function label
4. If it's ARM, detect if it's missing the thumb_func_start/arm_func_start prefix

Additional context

See discussion on Discord.